A fundamental shift is transforming the religious right, long a force in presidential politics, as aging evangelical leaders split on the 2008 race and a new generation of pastors turns away from politics altogether.

The result, in the short term, could be a boost for the centrist candidacy of former New York City Mayor Rudolph W. Giuliani, whose messy personal life and support for gay rights and legal abortion have not produced the unified opposition from Christian conservatives that many anticipated.

Over the longer term, the distancing of religious leaders from politics could prove even more consequential, denying the GOP one of the essential building blocks it has used to capture the White House in five of the last seven presidential races.

The shift is evident in this Rocky Mountain community at the heart of the evangelical movement.

"As far as me standing in the pulpit holding a voter guide, that's not going to happen," said the Rev. Brady Boyd, 40, who leads a congregation of 10,000 at New Life Church. He will use his position to teach the Bible to believers. "I won't use it to influence their vote," he said.

That suits many in his congregation just fine. "If he starts talking politics, that makes me very uneasy," said Wolfgang Griesinger, 56, a political independent.

"It's not his place to tell us who to vote for," said Marsha Thorson, 54, a Republican who is leaning toward Giuliani.

Black churches have a long tradition of political activism, mostly on the Democratic side. White evangelical churches did not assert themselves politically until Ronald Reagan's 1980 campaign, when first the Moral Majority and later the Christian Coalition began organizing on behalf of Republicans.

The term "evangelical" refers to Christians who claim a personal relationship with Christ and consider the Bible the word of God, to be faithfully obeyed. They are a huge group -- about one in four voters -- and far from monolithic; their ranks include Pentecostals, charismatics, Southern Baptists and many others. Some worship to rock music, others to hymns; some speak in tongues. Some believe God preordained those headed to heaven; others hold that anyone can achieve salvation by accepting Jesus Christ as their savior. Former Presidents Carter and Clinton are evangelicals, as is President Bush.

Despite that diversity, evangelicals have become a reliable -- and increasingly crucial -- Republican voting bloc. Many were drawn to Bush in 2000 because of his conservative stance on social issues and his story of turning to Christ to overcome a drinking problem. He won the support of more than eight in 10 Christian conservatives in 2000 and nearly nine of 10 in 2004, according to Los Angeles Times exit polls.

But in the three years since, many Christian conservatives have expressed a growing unease about the entanglement of politics and pulpit. Among young evangelical adults, nearly half say involvement in politics is problematic, according to a new book, "unChristian," from the evangelical research firm the Barna Group.

Some of that disillusionment comes from disappointment with Bush's policies, including the war in Iraq. But there's also shame at the often-bombastic, sharply partisan rhetoric of the traditional standard-bearers for conservative Christian values, including televangelist Pat Robertson, 77; the Rev. Jerry Falwell, who died this spring at age 73; and radio host James C. Dobson, 71.

One-third of evangelicals under 30 told Barna that they were embarrassed to call themselves believers.

"They're tired of the hard-edged politics that the Christian right has practiced in the last couple of generations," said John C. Green, senior fellow at the Pew Forum on Religion & Public Life. "They see all this division, all this anger, without a lot to show for it."

Mega-church pastors have capitalized on that frustration by offering a different brand of Christianity. With sunny, affirming services, they cast a broad welcome net -- and fill arena-size sanctuaries each Sunday.

They may promote a cause, such as AIDS relief in Africa. But endorse a candidate? Push a partisan agenda? That could empty half their pews. Few up-and-coming pastors want to risk such a backlash.

"There's nothing in it for them," said Timothy Morgan, deputy managing editor of the evangelical monthly Christianity Today. "It just gets people stirred up."

Florida pastor Troy Gramling, 40, recently preached a series he called "My Naked Pastor," which involved airing his every thought to webcams that followed him around the clock. Make that almost every thought: Gramling said he would never announce to his congregation of 14,000 how he planned to vote.

"That would be putting pressure on them to agree with me, and I don't feel I have a right to do that," Gramling said. "God doesn't call me and tell me who's his favorite."

Mega-church pastors often argue that Christians don't need big names to tell them whom to vote for; they need solid biblical teaching, which they can use to screen each candidate for proper values. But that leaves it up to the voters to determine which values should be the litmus test.

In previous years, the test was obvious: A godly leader must oppose abortion and gay rights and possess a strong Christian faith. This year, the evangelical establishment has sent voters a strong signal that they can feel free to branch away from that trinity.

Robertson, for instance, overlooked Giuliani's three marriages, his brief cohabitation with a gay couple, and his support for abortion rights to endorse him as the best candidate to fight terrorism.

Fundamentalist Bob Jones III, 68, made it clear that he believed that former Massachusetts Gov. Mitt Romney, a Mormon, follows a false religion. Yet Jones, chancellor of the university that bears his name, backed Romney on the grounds that he could win the White House.

Dobson has declined to endorse anyone -- despite repeated pleas from supporters of former Arkansas Gov. Mike Huckabee, an ordained Southern Baptist preacher who holds textbook religious right positions on social issues. Instead, Dobson has hinted that he may support a third-party candidate.

The disarray on the Christian right -- coupled with the striking silence of mega-church pastors -- means that Republicans can't count on the mass voter turnout drives that helped so much in years past.

"The days when Ralph Reed [and his Christian Coalition] could mobilize tens of thousands of followers are gone," said Rich Galen, an advisor to GOP presidential candidate Fred Thompson, a former senator from Tennessee. "In terms of suddenly turning on a spigot of funds and volunteers and direct mail, that just doesn't happen anymore."

Marvin Olasky, editor in chief of the Christian newsmagazine World, offers this perspective: "Anyone who talks about delivering the evangelical vote might as well apply for a job as a herder of cats."

The upheaval has also left an opening for Democrats, who are aggressively wooing evangelical voters by framing issues such as global warming, healthcare reform and the war in Iraq as moral priorities. Sens. Hillary Rodham Clinton of New York and Barack Obama of Illinois, the party's two presidential front-runners, discuss their faith openly and often, a notable contrast with past Democratic hopefuls.

The Democrats don't expect to swing the entire bloc of conservative religious voters their way next November. "But it's going to be such a close election that even 2 percentage points would make a huge difference," said D. Michael Lindsay, author of a new book on evangelical influence, "Faith in the Halls of Power."

Here at New Life Church, the congregation includes Democrats as well as independents and Republicans, and Boyd says he figures they all come to hear his take on the Gospel, not the latest Gallup poll.

"I don't think that as believers, as Christians, we should back away from the political scene. . . . But there's a correction happening now in the local church," he said.

New Life's founder, Ted Haggard, never hesitated to remind his congregation of his close ties to the Bush administration. Haggard resigned last year after encounters with a male prostitute, but the church's reputation as a political force remains; Boyd said he had been courted by several elected officials since arriving in Colorado Springs.

He meets with the politicians -- but only to see if he can offer them spiritual guidance.

The Nov. 2 election results followed a widely expected scenario. Republicans gained control of the House of Representatives, erasing what had been a 77-seat deficit. The GOP also made sizable gains in the Senate but fell short of total control of Capitol Hill.